We minimize (REF ) subject to () through an Alternating Minimization (AM) [1]}, wherein at each iteration, only one among \((\xi _{1, l}, \xi _{2, l}, \xi _{3, l}, \xi _{4, l})\)  is minimized while the rest are held fixed at values obtained at previous iteration or the previous step of the current iteration. This is summarized in steps
